The present invention relates to an electrostatic image developing toner used in electrophotography, electrostatic recording and electrostatic printing, and to a method for manufacturing thereof.
With the view of improving the flowability and stabilizing the electrification property of an electrostatic image developing toner used, for example, in electrophotography, inorganic fine particles such as silica fine particles are added in colored resin particles in the toner.
There has so far been known a technique to incorporate inorganic particles into colored resin particles by use of a fixed-container type batch mixer having high-speed stirring blades, such as Henschel mixer.
Such a mixer, however, has disadvantages that the peripheral speed is greatly different from the central portion near the rotation axis to the tips of the stirring blades, and that no stirring blades are present near the rotation axis, thereby the stirring force and dispersing force vary locally. As a result, inorganic particles are liable to be ununiformly dispersed on the surface of colored resin particles, lowering the flowability and electrification stability of a toner.
In order to solve such problems, there is proposed a sort of electro-magnetic hybrid technique, which comprises the steps of feeding colored resin particles and inorganic fine particles to a mixing zone holding working pieces (mixing medium) composed of rods of ferromagnetic material, and applying a shifting magnetic field to this mixing zone from the outside to have the working pieces begin random movement by means of the electromagnetic force due to the interaction with this shifting magnetic field. (Japanese Pat. O.P.I. Pub No. 291670/1987)